2.1 Earth's Crust in Motion

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vocabulary

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earthquake:the shaking and trembling that results from the movement of rock beneath the surface
stress:powerful forces that squeeze or pull the rock in the crust
shearing:stress that pulls two masses of rock in the opposite direction
tension:pulls on the crust
compression:squeezes rock until it folds or breaks
deformation:a change in the volume
fault:a break in Earth's crust
strike-slip fault:shearing makes a strike-slip fault
normal fault:tension makes normal faults
hanging wall:the top half of the fault
footwall:the bottom half of the fault
reverse fault:when the blocks move the other direction
fault-block mountain:normal faults raise up chunks of rock
Folds: to lay a part over or against another part
anticline:an arch of layers of rock in the Earth's crust
syncline:bends downward on the Earth's crust to form bowl shape
plateau:a large level area of high flat land

Outline

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Stress in the crust

• when there is too much stress between two plates a earthquake will happen
  • the energy can stay for a long time until it is released
• stress is a force and therefore adds energy to rocks
  • when the energy is stored inside the rock until it changes shape or breaks

Types of stress

• there is shearing, tension, compression
  • it takes millions of years to change the shape and volume
• other rocks may be softened by the heat from the sun or slowly bend like road tar
  • Shearing could cause rocks to separate into parts and slip, shearing may also cause the rock to change shape.

Kinds of faults

• the strike-slip fault, normal fault, reverse fault they are the main types of faults
• when there is too much stress that builds up in a rock, the rock may break, and that can create a faults

Strike-Slip Faults

• shearing is what makes strike-slip faults
• how strike-slip faults are made is when the ground on either side of the fault slip past each other sideways with some up and down process
  • strike-slip faults form boundaries between two plates that is called a transform boundary
• Example: The San Andreas fault in California is an example of a strike-slip fault and it is a transform boundary

Normal faults

• tension in Earth's crust may cause normal faults
• normal faults is at an angle so one pile of rocks lies above other piles that lie below the fault
  • tension create normal faults where plates diverge or they are pulled apart
• Example: normal faults occur along the Rio Grande rift valley in New Mexico, that is where two pieces of the Earth's crust are divergent

Reverse Faults

• compression forces make reverse faults
• its close to a normal fault but the hanging wall it above the foot wall
  • Example: Appalachian Mountains in the eastern United States that is part of a reverse fault
• over millions of years the hanging wall or the foot wall and one of them will have to overlap each other
  • that soon would wore away leaving only the mountain peaks

Friction along faults

• if two plates get stuck for a long time stress will build and when it is released big earthquake will happen

• if plates push against each other it will slowly push up and form a tall mountains